Stupefy some of the most unlikely people (4)
I believe the answer is:
stun
'stupefy' is the definition.
(I know that stupefy can be written as stun)
'some of the most unlikely people' is the wordplay.
'some of' indicates a hidden word.
'STUN' can be found hidden inside 'most unlikely people'.
(Other definitions for stun that I've seen before include "Concuss; amaze" , "Daze, stupify" , "Take aback" , "Daze, overwhelm" , "Bowl over" .)